Browsing by Author "Karakurt Cevik, Basak"

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    Characterization of Ambient Aerosols and Evolution of Organic Aerosol in Fort Worth, Houston and Centreville Alabama
    (2016-08-12) Karakurt Cevik, Basak; Griffin, Robert J
    The composition and concentration of submicron particulate matter (PM1) were measured by an Aerodyne high-resolution time-of-flight aerosol mass spectrometer at three locations: Dallas-Fort Worth (DFW), TX (June, 2011) Centreville, Al (June 1st –July 15th , 2013) and Houston, TX (May 12th -29th , 2015) to improve the understanding of the sources and transformation processes of PM1 components with an emphasis on Organic aerosol (OA) and relationships between secondary OA concentrations and various aging metrics in these three US cities. OA and sulfate aerosol were the most dominant PM1 components in all three sites. The DFW site was the cleanest with respect to PM pollution. The lowest concentrations of OA, sulfate, and total PM1 were observed at this site. Centreville, the most rural site, was characterized with the highest average concentrations of OA and total PM1. This indicates significant transport of material from urban locations and the influence of local biogenic VOC emissions. Houston site was characterized with frequent high peak events of organics and sulfate resulting from point source emissions. High OA events were mostly driven by emissions from Houston Ship Channel. OA in both DFW and Houston was apportioned into three OA factors including hydrocarbon-like OA, semi-volatile oxygenated organic aerosol (OOA) and low-volatility OOA. OA in Centreville was apportioned into four factors including isoprene-derived OA (IEPOX OA), biomass burning organic aerosol (BBOA), SVOOA, and LVOOA. This study uses a variety of aging metrics and their relations to OA/ΔCO and OA/ΔCO factor to characterize SOA. In DFW, LVOOA/ΔCO shows a positive correlation with sulfate aging metric and SVOOA/ΔCO shows an overall increase with nitrogen aging metric, indicating the different origin of the two OA factors, regional and local, respectively. In Centreville, a significant positive correlation is observed between LVOOA/ΔCO and the nitrogen aging metrics, which signifies the local characteristic of LVOOA at this site.
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    Comparison of estimates of airmass aging using particle and other measurements near Fort Worth, TX
    (2013-06-05) Karakurt Cevik, Basak; Griffin, Robert J.; Cohan, Daniel S.; Raun, Loren H.
    The composition, concentration, and size of submicron aerosols were measured with a time resolution of five minutes by an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) at a rural location northwest of the Dallas-Fort Worth, TX, area for the month of June 2011. A TSI, Inc., Model AE51 aethalometer using an optical absorption technique also was deployed to measure black carbon (BC) concentrations. The total measured PM1 mass concentration ranged between 1.0 µg/m3 and 17.1 µg/m3, with a mean and standard deviation of 4.6± 2.7 µg/m3. Significant variability is observed in the time series of total PM1 and of all four HR-ToF-AMS species, particularly between June 21 and 25. The average aerosol composition was dominated by organic matter (52.1 ± 14.8%) and sulfate (28.8 ± 11.8%). Organic aerosol concentrations were positively correlated with tracers of combustion carbon monoxide (CO) and BC, the coefficients of determination were r2=064 and r2=0.48, respectively. Because of the large influence of organics on total aerosol concentration, organic data were analyzed in the context of ΔOA/ΔCO, which typically is used to investigate the relative importance of secondary organic aerosol. The average ∆OA/∆CO for the data used was 64.0 ± 26.9 µg/ (m3 ppmv), which is typical of an aged air mass. Other metrics of age include the ratio of OOAI (more oxidized) to total oxidized organic aerosol (OOA), the ratio of sulfate to total sulfur, the ratio of its oxidation products to isoprene, and the ratio of nitrogen oxides to total reactive nitrogen. All metrics point to aged air masses, but variations in these age matrices, particularly during one period of enhanced ΔOA/ΔCO, help elucidate the contributions of various precursors and processes to organic aerosols at the site.